Servo governor having emergency control means



July 7, 1954 J. c. MCRoBERTs 3,139,892

SERVO GOVERNOR HAVING EMERGENCY CONTROL MEANS Filed Deo. 22, 1954 il rl.

United States Patent SERV() GOVERNR HAVING EMERGENCY CONTRGL MEANS JamesC. McRoberts, South Bend, Ind., assignor to The Bendix Corporation, acorporation of Delaware Filed Dec. 22, 1954, Ser. No. 477,036 7 Claims.(Cl. 137-18) This invention relates to an engine governor mechanism andmore specifically to a proportional type governor having a power drivengovernor valve particularly adapted for use in a fuel feed system forgas turbine engines.

Direct acting type governors, have heretofore enjoyed the advantage ofrelative simplicity over power driven governors controlled byservo-mechanisms. Direct acting governors have, however, certaininherent disadvantages such as susceptibility to dirt or other foreignparticles in the fuel which may cause sticky governor action, a tendencytowards dynamic or static hydraulic pressure unbalance across thegovernor valve, governor valve hysteresis if valve clearances are keptreasonably close so as to minimize fuel leakage at the ends of thevalve, a relatively large gravity or G" effect due to the necessaryrelatively large mass of the governor parts, and substantially less thanoptimum response time. On the other hand, servo-operated governors haveheretofore generally suffered disadvantages such as undue complexity,and the lack of a direct acting standby or emergency governor controlmeans automatically operative in case of a failure of theservoameehanism.

In application Serial No. 446,335, filed July 28, 1954 in the name ofAndrew A. Kuzmitz (common assignee), now abandoned, in favor ofcontinuation application Serial No. 682,570, filed September 5, 1957there is disclosed and claimed a relatively simple servo type governorwhich avoids or tends to minimize all of the above mentioneddisadvantages to which both direct acting governors and servo actuatedgovernors have heretofore been subject. My invention constitutes animprovement of the governor mechanism disclosed in said application.

It is therefore a primary object of this invention to provide animproved servo type governor which avoids or minimizes all of the abovementioned disadvantages to which both direct acting governors 'and servoactuated governors have heretofore been subject.

Another important object of this invention is to provide a highlycompact and relatively simple servo governor which provides improvedstandby or emergency governor control means automatically operative incase of a failure of the servo-mechanism.

The foregoing and other objects and advantages will become apparent inview of the following description taken in conjunction with thedrawings, wherein:

FIGURE 1 is a sectional View of a turbo-jet engine equipped with a fuelfeed and power control device which includes the applicants governor;and

FIGURE 2 is a :schematic sectional view of a govenor in accordance withthe invention.

Referring now to FIGURE 1, a gas turbine engine is generally indicatedat numeral 10 and includes a series of annularly disposed combustionchambers 11 mounted in a casing having a header or air intake section12, and a compressor 13, shown as of the aXial flow type, which isdriven by means of a turbine 14 through a shaft 15. Each of thecombustion chambers is provided with a burner nozzle 16 to which meteredfuel is supplied under pressure by way of a conduit 17, a fuel manifold18 and individual fuel lines 19. The conduit 17 receives meteredfuelfrom a fuel control device generally indicated at 20, said deviceincluding the applicants governor as shown in FIGURE 2. A pump 22 of thepositive displacement type supplies fuel under pressure to fuel controlthrough 3,139,892 Patented July 7 1964 ice a conduit 24, a portion ofwhich fuel may be by-passed back to the pump inlet through a conduit 26.

Referring now to FIGURE 2, a governor housing is shown at 40 whichcontains a hollow sleeve member 42 held in iXed position therein betweenhousing abutments 44 and 46, and which defines a chamber 48 in which ishoused governor control mechanism, to be hereinafter described. Annularinlet and outlet chambers and 52, respectively, are formed between thesleeve member and the housing, and are respectively connected to fuelinlet conduit 24 at a pressure P1 and to fuel outlet conduit 17 at apressure P2, communication between said annular chambers being effectedby a plurality of annularly arranged inlet ports 54 and outlet ports 56formed in the sleeve member, and by a governor chamber 58 formed betweenthe sleeve member and a governor valve 60 which is reciprocable therein.

The governor valve 60 includes a hollow outer valve stem 62 formedintegrally with cup-shaped piston like elements 64, 66 and 68, whichelements are arranged in fixed spaced relation to each other to define,along with sleeve member 42 and outer valve stem 62, the governorchamber 58, a regulated pressure chamber 70, a servo pressure chamber'72 and a pump inlet pressure chamber 74. A hollow inner valve stem 76is suitably connected to element 68 at 78, and terminates at the leftend thereof in a tapped section 80 which receives a stud 82 movablebetween an adjustable minimum fuel flow stop 84 and a bifurcatedvariable maximum fuel flow stop 86 in a chamber 88 formed within ahousing cover plate 90.

The inner valve stem 76 defines a fuel leakage flow passage 92, whichconnects governor chamber 58 and servo pressure chamber 72 to by-passconduit 26 by way of annular valve clearance passages 94 and 96, anannular chamber 98 formed within the valve metering element 64, apassage and chamber 10i) and 102, respectively, also formed within valveelement 64, a passage 104, pump inlet pressure chamber 74, and a conduit106. An annular passage 108 is formed between inner valve stem 76 andouter valve stem 62 and connects annular chamber 50 to conduit 26 by wayof a conduit 110 having a constant discharge pressure regulator valve112 therein, the regulated pressure chamber 70, ports 114 formed inouter valve stem 62 between piston elements 66 and 68, a passage andrestriction 116 and 118 in valve element 64, the servo pressure chamber72, valve stem passages 120 and 122, a servo valve orifice member 124, aservo valve chamber 126 formed within a ported cup-shaped member 128, achamber 132 formed within a stepped-down cylindrical extension 134 ofsleeve member 42, a plurality of annularly arranged ports 136 formed insleeve extension 134, the chamber 48, and a conduit 140.

The governor control mechanism housed within chamber 48 includes a pairof centrifugal weights 142 which are pivotally mounted on brackets 144and which are adapted to be rotatably driven by the engine by means of abevel gear 146, a geared member 148, a bevel gear in mesh with one endof member 148, and a governor drive shaft 152, on one end of which ismounted the gear 150 and on the opposite end of which is mounted adriveplate 154 to which brackets 144 are attached. The centrifugalweights 142 are made integral with foot members 156, which yare adaptedto continuously abut a spring retainer member 158 resiliently connectedto a governor spring setting member 160 by a governor spring 162. Springsetting member 160 is slidably mounted on the outer surface of sleeveextension 134 and may be actuated in an axial direction to vary thedegree of compression of governor spring 162 by means of a bifurcatedgovernor lever 164, suitably mounted in the left end of chamber 48 andactuable by means of a pilot control lever, notV shown, which isconnected thereto by a link 166, a lever 168 and a shaft 170 (see FIGURE1). Spring retainer member 158 is connected to the servo valve member128 by means of a rod 172, on which is mounted a guide land 174, saidmember 128 providing a housing for the orifice member 124 and a floatinghalf-ball type servo valve 176. An annular lip 178 is formed on the leftend of member 128.

A highly compact, efficient, and relatively simple servotype governormechanism may be designed in accordance with the foregoing descriptionof structure if, as is preferred, all of the major elements which aremounted for relative movement with respect to sleeve member 42,including governor valve means 60, servo valve and orifice means 176,124, and the centrifugal weight mounting plate 154, are arranged insubstantial coaxial relation with each other.

During operation, valve element 64 of governor valve 60 is positionallycontrolled within sleeve member 42 to vary the effective area ofmetering valve ports 54, by the governer mechanism contained withinchamber 48 during any given pilot selected condition of steady stateengine operation and during governor cut-off operation, by the maximumHow-valve stop 86 during acceleration of the engine prior to governorcut-off action, and by the fixed minimum valve stop 84 during conditionsof engine deceleration.

The fuel metering pressure differential across metering ports 54 ispreferably maintained at a constant value irrespective of variations inengine operating conditions by constant pressure differential regulatorvalve means, not shown, which is preferably of the type disclosed in thecopending application of Harry C. Zeisloft, Serial No. 168,294 filedDecember 22, 1961, which is a division of application Serial No. 684,368filed September 16, 1957, now abandoned, which in turn is acontinuationin-whole of application Serial No. 248,402, filed September26, 1951 (common assignee) also now abandoned.

The position of the maximum valve stop 86 is continuously controlled asa function of certain existing engine operating parameters or variables,such as engine speed and compressor inlet temperature, by mechanism suchas is disclosed and claimed in the copending application of Harry C.Zeisloft, supra, said stop being effective during an acceleration of theengine to a new selected speed to override the `instantaneous speedchange demand of the pilot and independently control the rate of openingmovement of vaive 60 to limit the rate of change of fuel ow inaccordance with certain engine parameters or variables up to theselected speed, at which speed the governor mechanism shown in chamber43 functions to cause a closing movement of valve 60 until a steadystate condition of operation exists, as more fully hereinafterexplained.

Assume that the engine has been started and accelerated to a conditionof equilibrium or steady state operation in the mid-speed range. Theselection of the assumed condition of engine operation is controlled bythe pilot who, by means of a control lever, link 166 and lever 168, mayactuate the bifurcated governor lever 164 and spring setting member 160to compress the governor spring 162 a predetermined amount, therebyselecting a desired engine speed. At the assumed condition ofequilibrium, the force generated by the governor weights 142 exactlybalances the governor spring force, in which condition the servo valvehousing 128 maintains the half-ball servo valve 176 in a fixed positionwith respect to orifice member 124. This results in a fixed arearelationship between restriction 118 and orifice 124 which maintains avalue of pressure PS in servo pressure chamber 72, to establish a fixedposition of valve element 64 with respect to ports 54. The parts asshown in FIG- URE 2 are positioned relative to each other to illustratethe condition of equilibrium operation such as above described; i.e.valve control stud 82 is oating between the maximum and minimum valvestops, the centrifugal weight force output is in balance with governorspring 162, and servo valve 176 is positioned with respect to orificemember 124 to equilibrate the valve closing force resulting fromcontrolled servo pressure PS with the valve opening force resulting fromregulated pressure PR.

In practice, it has been found that very good valve response time andvalve stability are attained if the ratio of the net valve area in servopressure chamber 72 to the net area in regulated pressure chamber '70 ismade approximately two to one, and the diameter of restriction 118 ismade approximately .028. This valve area ratio and bleed diametercombination has been found to result in almost instantaneous valveresponse, following movement of servo valve 176, without valve overshootor undershoot at equilibrium. Obviously, many other valve area ratio andbleed size combinations may be designed to satisfy certain valveresponse and stability requirements, and my invention is in no senserestricted to the above exemplary combination. However, the bleed 118should be held within a certain predetermined range of diameters; if itis too small in diameter good valve stability, but poor response timeand dirt problems will result, whereas if the bleed is too large,instantaneous response, but poor stability will result.

If the pilot should desire to accelerate the engine to a higher speedfrom the aforementioned equilibrium condition, he will actuate lever 168in a direction to move governor lever 164 rightwardly to compressgovernor spring 162, thereby actuating servo valve 176 in an opendirection with respect to orifice member 124 to upset the equilibrium ofthe governer, which results in a sudden decrease in PS pressure due tothe increased area ratio between the orifice 124 and bleed 118 andopening movement of governor valve 60 until limited by contact betweenacceleration lever 86 and stud 82. The acceleration lever 86 iscontrolled by mechanism, not shown, in such a manner that the rate ofopening movement of governor valve 60 controls fuel ow so as to avoid anovertemperature condition at the turbine inlet and compressor surge orstall at a given altitude. During such a transient condition the forceof pressure PS on valve 60 is insufficient to balance the constant netforce of the regulated pressure PR acting on said valve, and fuel ow isincreased at a rate which is a function of the rate of change ofposition of acceleration lever 86 until the speed selected by the pilotis attained.

As the engine approaches selected speed, the force output of weights 142begins to overcome the governor spring 162 and actuates servo valve 176leftwardly to produce governor valve cut-off action as said weights fiyoutwardly about their pivots. It is apparent that during such cut-offaction the governor valve follows the movement of servo valve 176, andwhen equilibrium is reached between weights 142 and spring 162 saidservo valve has established that amount of leakage through orificemember 124 which is necessary to equilibrate the net PS and PR pressureforces, whereby a fixed position of the governor valve is maintained.

The valve leakage circuit 98, 180, 92, 104, 74 and 106 is provided sothat fuel at P1 pressure cannot flow past valve 60 into the servopressure chamber to vary the valueof PS pressure in an undesirablemanner. With this arrangement, Ps pressure will vary solely as afunction of the area ratio between restriction 118 and the orificemember 124.

My invention affords an improved mechanical control arrangement for thegovernor valve 60 in the event that the servo system fails for anyreason. lf, for example, the pressure regulator valve 112 should fail inclosed position, pressures PR and PS would both decrease to the value ofpump inlet pressure as a result of pressure bleed-off from chambers 7)and 72 to chamber 48. As a result of this drop in pressure in chambers70 and 72 a balance of the sum of hydraulic forces acting on valve 68 iseffected. In other words, under such conditions, no net force externalto the governor mechanism contained in chamber 48, except the smallfrictional force between the valve 60 and sleeve 42, acts on valve 6l).

It may therefore be seen that valve 60 is, under such conditions,subject to direct mechanical control by the governor mechanism inchamber 48 without appreciably affecting the operation thereof. My servopowered governor may therefore be said to fail safe; i.e. the governoris designed such that the normal hydraulic connection between thegovernor mechanism in chamber 48 and governor valve 60 becomes amechanical connection in the event that the servo system fails; thepilot may still select the same engine operating speeds throughout thepermissible range thereof at pilot leverpositions corresponding to thoseat said speeds before the servo failure by actuating resetting member160 to compress or relax the governor spring, thereby moving lip 178 ofservo valve housing 12S into contact with orifice member 124, or servovalve 176 into contact therewith, which manually actuates valve 60 in anaccelerating or decelerating direction, respectively. When the enginereaches a new selected speed during acceleration, the weights 142overcome governor spring 162 and actuate servo valve 176 into contactwith orifice member 124 to mechanically move governor valve 60 in a fuelflow decreasing direction until the governor mechanism is inequilibrium, at which time the engine is operating in a steady statecondition at the new selected speed.

Contrariwise, as the engine reaches a new selected speed during adeceleration of the engine, the force output of the governor springbegins to overcome the decreasing force output of the centrifugalweights and actuates the lip 17 8 of servo valve housing 128 intocontact with orifice member 124 to mechanically move governor valve 6i)in a fuel flow increasing direction until the governor mechanism is inequilibrium, at which time the engine is operating in a steady statecondition at the new selected speed.

From the above it is apparent that my invention provides a highlycompact servo type engine governor which is designed in such a mannerthat a failure of the servo system does not cause any loss of enginecontrol.

Although only one specific embodiment of my invention has beendescribed, it will be apparent to those skilled in the art that certainvariations in design and relative arrangement of parts may be madewithout departing from the scope of the invention.

I claim:V

l. An engine speed governor comprising an engine speed responsivedevice, operator controlled means for adjusting said device to select anoperating speed for the engine, servo valve means controlled by saiddevice, governor valve means having an associated differential areapiston means, a regulated pressure fluid source communicating with saidpiston means to supply a first actuating pressure thereto, passage meanscontaining a restriction therein connected to said fluid source andoperable to transmi a second actuating pressure to said piston means,said first and said second actuating fluid pressures acting incombination to comprise a pressure differential oper-able to controlsaid differential area piston means, said servo valve means beingadapted to vary said pressure differential during a transit in enginespeed and to fix said pressure differential during equilibrium operationof the engine at any given speed selected at said operator controlledmeans, and said servo valve means and said engine speed responsivedevice being so constructed and arranged with respect to said governorvalve means that a predetermined decrease in said pressure differentialcauses said governor valve means to become mechanically connected tosaid engine speed responsive device for the purpose of controlling thespeed of the engine in an increasing and decreasing direction.

2. An engine speed governor comprising governor valve means forcontrolling the flow of motive fluid to the engine including pistonmeans responsive solely to fluid pressure forces during normal operationof the governor, a regulated fluid pressure source communicating withsaid piston means to provide a substantially constant fluid pressureacting on said piston means for moving said valve means in an openingdirection, passage means including a restriction therein also connectingsaid fluid pressure source with said piston means to provide a variablefluid pressure for moving said valve means in a closing direction, andan engine speed responsive device operatively connected to said governorvalve means, said operative connection including servo valve means forcontrolling said Variable fluid pressure, said device being soconstructed and aI- ranged relative to said governor valve means that amechanical connection is effected therebetween following a predeterminedchange in said variable fluid pressure.

3. An engine speed governor comprising governor valve means forcontrolling the flow of motive fluid to the engine includingdifferential area piston means, first and second chamber means formed onopposite sides of said piston means, a fluid source containing a fluidof substantially constant pressure, means for conducting thesubstantially constant pressure fluid from said source to said firstchamber, restrictive pass-age means connecting said first and secondchambers to transmit fluid to said second chamber, and an engine speedresponsive mechanism normally hydraulically connected to said governorvalve means for controlling the fluid pressure in said second chamberand for effecting a mechanical connection with said governor valve meansfollowing a predetermined change of fluid pressures in said first andsecond chamber relative to each other.

4. An engine speed A governor as claimed in claim 3 wherein said enginespeed responsive device is arranged in substantially coaxial relationwith said governor valve means.

5. In a fuel feed and power control system for an internal combustionengine, a fuel conduit for conducting fuel to the engine, a fuelmetering restriction in said conduit, reciprocal governor valve m'eansfor controlling the flow of fuel through said restriction, said valvemeans including first and second valve elements directly responsive tofluid pressures, a regulated fluid pressure source containing fluid at afirst pressure communicating with said valve element, restrictivepassage means operable to transmit fluid from said first to said secondvalve element at a second pressure, control means for controlling thelevel of said second pressure, with said control means including a servocontrol valve operative with a servo orifice mem- -ber for controllingthe movement of said valve means, said control means including a housingmember for said servo valve, with said housing member being adapted tomove said orifice member in the event said servo valve becomesinoperative with regard to controlling the movement of said valve means,and an engine speed responsive mechanism connected to said control meansfor maintaining a given pressure difference between said first andsecond fluid pressures during equilibrium operation of the engine at anygiven speed.

6. Control apparatus comprising: a housing having an interior chamberformed therein; a differential area piston member having a large and asmall area piston element; said differential area piston memberoperative to divide said chamber into first and second compartments onopposed sides of said piston member; said small area and large areapiston elements being spaced at opposed piston sides to communicate withsaid first and second compartments respectively; a high pressure controlfluid source; first passage means interconnecting said source and saidrst compartment; constant pressure regulating means disposed in saidfirst passage and operative to regulate the control fluid pressuresupplied to said first compartment to a substantially constant value;second passage means including a ilo'fw restriction therein formed insaid differential area piston member to interconnect said first andsecond compartments and provide servo control fluid to said secondcompartment; an elongated stem member secured to said large pistonelement and movable therewith; said stem member extending through andexteriorly of said second compartment; third passage means formed withinsaid elongated stem having a rst opening formed in said stem within saidsecond compartment; said third passage means having a second openingformed in said stem exteriorly of said second compartment at the end ofsaid stem to provide a servo control orice; and a servo control valvemember operative with said servo control orice to control the flow fromand pressure of control fluid in said second compartment and therebycontrol the pressure balance which controls the motion of saiddifferential area piston member.

7. Control apparatus as claimed in claim 6 wherein said servo controlvalve member is of the halfJball type; `a cup shaped member forpositioning said half-ball servo valve; said cup member including lipprojections engageable with said elongated stem member to mechanicallyposition said 0 differential area piston in event of loss of uidpressure in said second compartment.

References Cited in the le of this patent UNITED STATES PATENTS 162,782Westinghouse May 4, 1875 991,230 Noyes May 2, 1911 1,339,939 Alter May1l, 1920 2,371,793 Bourland Mar. 20, 1945 2,466,358 Besserdich Apr. 5,1949 2,644,513 Mock July 7, 1953 2,646,813 Mueller July 28, 19532,669,973 Parker Feb. 23, 1954 2,711,158 Leduc June 21, 1955 FOREIGNPATENTS 111,487 Germany June 23, 1900 309,307 Germany Nov. 16, 1918556,079 France Apr. 6, 1923

5. IN A FUEL FEED AND POWER CONTROL SYSTEM FOR AN INTERNAL COMBUSTIONENGINE, A FUEL CONDUIT FOR CONDUCTING FUEL TO THE ENGINE, A FUELMETERING RESTRICTION IN SAID CONDUIT, RECIPROCAL GOVERNOR VALVE MEANSFOR CONTROLLING THE FLOW OF FUEL THROUGH SAID RESTRICTION, SAID VALVEMEANS INCLUDING FIRST AND SECOND VALVE ELEMENTS DIRECTLY RESPONSIVE TOFLUID PRESSURES, A REGULATED FLUID PRESSURE SOURCE CONTAINING FLUID AT AFIRST PRESSURE COMMUNICATING WITH SAID VALVE ELEMENT, RESTRICTIVEPASSAGE MEANS OPERABLE TO TRANSMIT FLUID FROM SAID FIRST TO SAID SECONDVALVE ELEMENT AT A SECOND PRESSURE, CONTROL MEANS FOR CONTROLLING THELEVEL OF SAID SECOND PRESSURE, WITH SAID CONTROL MEANS INCLUDING A SERVOCONTROL VALVE OPERATIVE WITH A SERVO ORIFICE MEMBER FOR CONTROLLING THEMOVEMENT OF SAID VALVE MEANS, SAID CONTROL MEANS INCLUDING A HOUSINGMEMBER FOR SAID SERVO VALVE, WITH SAID HOUSING MEMBER BEING ADAPTED TOMOVE SAID ORIFICE MEMBER IN THE EVENT SAID SERVO VALVE BECOMESINOPERATIVE WITH REGARD TO CONTROLLING THE MOVEMENT OF SAID VALVE MEANS,AND AN ENGINE SPEED RESPONSIVE MECHANISM CONNECTED TO SAID CONTROL MEANSFOR MAINTAINING A GIVEN PRESSURE DIFFERENCE BETWEEN SAID FIRST ANDSECOND FLUID PRESSURES DURING EQUILIBRIUM OPERATION OF THE ENGINE AT ANYGIVEN SPEED.